MIXED CARBON DIOXIDE-KRYPTON SOLIDS - A NEW DILUTED QUADRUPOLE SYSTEM

Mixtures of carbon dioxide and krypton gases were codeposited from the gas phase. The resulting solids were studied by X-ray powder diffract ion and IR absorption. Molecular dynamics simulation was applied to th e system. Under equilibrium conditions phase separation occurs. If dif fusion is suppressed, solids with extremely short coherence lengths we re found in the concentration range of 30-70 mol% Kr. The simulation a llows to reproduce this disorder. It is due to internal distortions ra ther than to grain size effects. The addition of krypton reduces the q uadrupole-quadrupole interaction. This leads to orientational and to c entre-of-gravity disorder. The properties of CO2:Kr are discussed in c omparison with the well known quadrupole glass N-2:Ar For the molecula r dynamics simulation a flexible model of the CO2 was adopted. This al lowed to reproduce the influence of the local environment on the band shape of the bending mode nu(2).